As shown by FIG. 10 and FIG. 11, generally, an electric stapler of this kind is constituted by a cartridge 32 charged with a number of staples and attachable to and detachable from a magazine portion 31 of a main body case 30, a driver mechanism 33 for striking out the staple at inside of the cartridge 32 from the magazine portion 31 by being driven by a motor provided at inside of the main body case 30, and a table 35 arranged to be opposed to a portion 34 for striking out the staple by the driver mechanism 33 and pivotably supported by a side plate constituting the main body frame 30 for striking out the staple charged in the magazine portion 31 to sheets of paper P to be bound arranged between the magazine portion 31 and the table 35 from the magazine portion 31 by driving the driver mechanism 33 by driving the motor and folding to bend a front end of a leg of the staple penetrated through the sheets of paper to be bound by a clincher 36 arranged on the table 35.
Normally, the table 35 is arranged to be remote from the staple striking portion 34 of the magazine portion 31 and is operated to pivot to pinch the sheets of paper P to be bound between the table 35 and an upper face of the magazine portion 31 before inserting the sheets of paper to be bound and striking out the staple by the driver mechanism 33. Although the table 35 needs to support a lower face side of the sheets of paper to be bound against a binding load generated during a time period in which the leg of the staple struck out from the magazine portion 31 by the driver mechanism 33 penetrates the sheets of paper to be bound and is folded to bend along a rear face of the sheets of paper to be bound by the clincher 36 formed at a front end portion of the table 35, since an operating stroke of the table 35 is varied in accordance with a thickness of the sheets of paper to be bound, the table 35 cannot directly be driven to pivot by a cam, a link mechanism or the like, and the table 35 is operated by interposing a spring force at the cam or the link mechanism. However, in order to support the binding load which normally becomes about 8 through 10 Kg, a spring of a large load is needed, and a drive mechanism for driving the table 35 by way of the large spring load is enlarged to constitute a factor of hampering small-sized formation of the electric stapler for being included in a copier or the like.
Hence, as shown by FIG. 10 and FIG. 11, there is disclosed a lock mechanism of the table for fixing the table 35 at a closing position by a wedge member fitted to a portion of the table 35 operated by a spring urge force in a direction of pinching the sheets of paper P to be bound in JP-A-2001-191265 or the like. The lock mechanism of the table is constituted by the table 35 a rear end portion of which is pivotably supported by a pivotal support shaft 38 and urged in the closing direction by a torsional coil spring 39, an operating link 40 for holding the table 35 at an opening position, and a wedge member 37 engaged with the table 35 for hampering the table 35 from being pivoted in the opening direction.
Normally, before operating the electric stapler, a support portion 41 formed at the operating link 40 is engaged with a fixed shaft 42 integrally pivoted with the table 35 to hold the table 35 at the opening position, and when the sheets of paper P to be bound is mounted on an upper face of the magazine portion and the electric stapler is operated, engagement of the support portion 41 and the fixed shaft 42 is released by operating the operating link 40 in cooperation with the driver mechanism 33 for striking out the staple to operate the table 35 in a binding direction by the torsional coil spring 39 to pinch the sheets of paper P to be bound arranged between the table 35 and the magazine portion 31. In accordance with operation of the table 35, the wedge member 37 is slid to move by the spring force to engage a locking portion 43 formed at the wedge member 37 with the fixed shaft 42 pivoted integrally with the table 35 to thereby hamper the table 35 from being pivoted in the opening direction to lock at the closing position.
According to the above-described mechanism, the wedge member 37 is slidably held by the main body case 30, the wedge member 37 is slid to move by the spring urge force to engage with the fixed shaft 42 integral with the table 35 to lock the table 35 at the closing position and therefore, no problem is posed since when a range of varying the thickness of the sheets is small, a range of varying a pivotal stroke of the table 35 is comparatively small. However, in the case that a maximum number of sheets for an electric stapler to bind the sheets of paper P is large, the range of the operating stroke of the table 35 is increased, a distance of sliding to move the wedge member 37 is obliged to set to be large, and small-sized formation of the electric stapler cannot be achieved. Further, the wedge member is engaged with the fixed shaft 42 arranged at a vicinity of the pivotal support shaft 38 pivotably supporting the table 35 and therefore, although the wedge member can be adopted in a small-sized stapler which does not produce a large binding load, locking cannot sufficiently be carried out for a large-sized stapler generating a large binding load at a front end side of the table 35.